The mechanism of the phototoxicity of alpha-terthienyl is being studied. The proposed research will focus on: a) the structure determination of one photoproduct of alpha-terthienyl observed at 350 nm; b) whether the binding to alpha-terthienyl affects singly or doubly stranded DNA; c) whether nuclear or mitochondrial DNA is affected; d) the location of the site(s) of attachment of alpha-terthienyl to DNA; e) the initiation of biochemical studies with polyacetylenes related to alpha-terthienyl.